Hey
I usually write on the free spaces on that page so that when you revise you can see them and dont have to reach out for points.
You will always find some free spaces around in a page. Just write imp notes. Also when you read and write it becomes easy to remember the notes.

Or make Flash cards or write down in a book.

And about what you shld take as notes. No way, take down what ever you feel is necessary.

To make it fun, draw some pics to signify traps and discoveries!!